diff --git a/src/Nethermind/Nethermind.Merge.Plugin.Test/BlockTreeTests.cs b/src/Nethermind/Nethermind.Merge.Plugin.Test/BlockTreeTests.cs
index de7f0a7f2ec..f0729dff70a 100644
--- a/src/Nethermind/Nethermind.Merge.Plugin.Test/BlockTreeTests.cs
+++ b/src/Nethermind/Nethermind.Merge.Plugin.Test/BlockTreeTests.cs
@@ -20,6 +20,7 @@
 using Nethermind.Merge.Plugin.Synchronization;
 using Nethermind.Serialization.Rlp;
 using Nethermind.Specs;
+using Nethermind.Specs.ChainSpecStyle;
 using Nethermind.Specs.Forks;
 using Nethermind.Synchronization.Blocks;
 using Nethermind.Synchronization.Peers;
@@ -76,7 +77,7 @@ public void Can_suggest_terminal_block_correctly()
             .WithSpecProvider(specProvider)
             .OfChainLength(10)
             .TestObject;
-        PoSSwitcher poSSwitcher = new(new MergeConfig(), new SyncConfig(), new MemDb(), tree, specProvider, LimboLogs.Instance);
+        PoSSwitcher poSSwitcher = new(new MergeConfig(), new SyncConfig(), new MemDb(), tree, specProvider, new ChainSpec(), LimboLogs.Instance);
 
         Block? block8 = tree.FindBlock(8, BlockTreeLookupOptions.None);
         Assert.False(block8!.IsTerminalBlock(specProvider));
@@ -95,7 +96,7 @@ public void Suggest_terminal_block_with_lower_number_and_lower_total_difficulty(
             .WithSpecProvider(specProvider)
             .OfChainLength(10)
             .TestObject;
-        PoSSwitcher poSSwitcher = new(new MergeConfig(), new SyncConfig(), new MemDb(), tree, specProvider, LimboLogs.Instance);
+        PoSSwitcher poSSwitcher = new(new MergeConfig(), new SyncConfig(), new MemDb(), tree, specProvider, new ChainSpec(), LimboLogs.Instance);
 
         Block? block7 = tree.FindBlock(7, BlockTreeLookupOptions.None);
         Block newTerminalBlock = Build.A.Block
@@ -124,7 +125,7 @@ public void Cannot_change_best_suggested_to_terminal_block_after_merge_block()
             .OfChainLength(10)
             .TestObject;
 
-        PoSSwitcher poSSwitcher = new(new MergeConfig(), new SyncConfig(), new MemDb(), tree, specProvider, LimboLogs.Instance);
+        PoSSwitcher poSSwitcher = new(new MergeConfig(), new SyncConfig(), new MemDb(), tree, specProvider, new ChainSpec(), LimboLogs.Instance);
 
         Block? block8 = tree.FindBlock(8, BlockTreeLookupOptions.None);
         Assert.False(block8!.Header.IsTerminalBlock(specProvider));
diff --git a/src/Nethermind/Nethermind.Merge.Plugin.Test/EngineModuleTests.Setup.cs b/src/Nethermind/Nethermind.Merge.Plugin.Test/EngineModuleTests.Setup.cs
index 982c5a1741b..25b5bfe2f0f 100644
--- a/src/Nethermind/Nethermind.Merge.Plugin.Test/EngineModuleTests.Setup.cs
+++ b/src/Nethermind/Nethermind.Merge.Plugin.Test/EngineModuleTests.Setup.cs
@@ -20,6 +20,7 @@
 using Nethermind.Core.Crypto;
 using Nethermind.Core.Specs;
 using Nethermind.Core.Test.Blockchain;
+using Nethermind.Core.Test.Builders;
 using Nethermind.Core.Timers;
 using Nethermind.Crypto;
 using Nethermind.Db;
@@ -33,6 +34,7 @@
 using Nethermind.Merge.Plugin.Handlers;
 using Nethermind.Merge.Plugin.Synchronization;
 using Nethermind.Specs;
+using Nethermind.Specs.ChainSpecStyle;
 using Nethermind.Specs.Forks;
 using Nethermind.State;
 using Nethermind.Synchronization.ParallelSync;
@@ -236,7 +238,7 @@ protected override IBlockProcessor CreateBlockProcessor()
         protected IBlockValidator CreateBlockValidator()
         {
             IBlockCacheService blockCacheService = new BlockCacheService();
-            PoSSwitcher = new PoSSwitcher(MergeConfig, SyncConfig.Default, new MemDb(), BlockTree, SpecProvider, LogManager);
+            PoSSwitcher = new PoSSwitcher(MergeConfig, SyncConfig.Default, new MemDb(), BlockTree, SpecProvider, new ChainSpec() { Genesis = Core.Test.Builders.Build.A.Block.WithDifficulty(0).TestObject }, LogManager);
             SealValidator = new MergeSealValidator(PoSSwitcher, Always.Valid);
             HeaderValidator preMergeHeaderValidator = new HeaderValidator(BlockTree, SealValidator, SpecProvider, LogManager);
             HeaderValidator = new MergeHeaderValidator(PoSSwitcher, preMergeHeaderValidator, BlockTree, SpecProvider, SealValidator, LogManager);
diff --git a/src/Nethermind/Nethermind.Merge.Plugin.Test/MergeRewardCalculatorTests.cs b/src/Nethermind/Nethermind.Merge.Plugin.Test/MergeRewardCalculatorTests.cs
index 8175a677e5f..3c49333bdaa 100644
--- a/src/Nethermind/Nethermind.Merge.Plugin.Test/MergeRewardCalculatorTests.cs
+++ b/src/Nethermind/Nethermind.Merge.Plugin.Test/MergeRewardCalculatorTests.cs
@@ -10,6 +10,7 @@
 using Nethermind.Logging;
 using Nethermind.Merge.Plugin.Handlers;
 using Nethermind.Specs;
+using Nethermind.Specs.ChainSpecStyle;
 using Nethermind.Specs.Forks;
 using NSubstitute;
 using NUnit.Framework;
@@ -156,7 +157,7 @@ private static PoSSwitcher CreatePosSwitcher()
             specProvider.TerminalTotalDifficulty = 2;
             MergeConfig? mergeConfig = new() { };
             IBlockCacheService blockCacheService = new BlockCacheService();
-            return new PoSSwitcher(mergeConfig, new SyncConfig(), db, blockTree, specProvider, LimboLogs.Instance);
+            return new PoSSwitcher(mergeConfig, new SyncConfig(), db, blockTree, specProvider, new ChainSpec(), LimboLogs.Instance);
         }
 
     }
diff --git a/src/Nethermind/Nethermind.Merge.Plugin.Test/PoSSwitcherTests.cs b/src/Nethermind/Nethermind.Merge.Plugin.Test/PoSSwitcherTests.cs
index 9f2992c46ed..1c1b5838b21 100644
--- a/src/Nethermind/Nethermind.Merge.Plugin.Test/PoSSwitcherTests.cs
+++ b/src/Nethermind/Nethermind.Merge.Plugin.Test/PoSSwitcherTests.cs
@@ -30,7 +30,7 @@ public void Initial_TTD_should_be_null()
         {
             UInt256? expectedTtd = null;
             IBlockTree blockTree = Substitute.For<IBlockTree>();
-            PoSSwitcher poSSwitcher = new(new MergeConfig(), new SyncConfig(), new MemDb(), blockTree, TestSpecProvider.Instance, LimboLogs.Instance);
+            PoSSwitcher poSSwitcher = new(new MergeConfig(), new SyncConfig(), new MemDb(), blockTree, TestSpecProvider.Instance, new ChainSpec(), LimboLogs.Instance);
 
             Assert.That(poSSwitcher.TerminalTotalDifficulty, Is.EqualTo(expectedTtd));
         }
@@ -45,7 +45,7 @@ public void Read_TTD_from_chainspec_if_not_specified_in_merge_config()
             ChainSpec chainSpec = loader.Load(File.ReadAllText(path));
 
             ChainSpecBasedSpecProvider specProvider = new(chainSpec);
-            PoSSwitcher poSSwitcher = new(new MergeConfig(), new SyncConfig(), new MemDb(), blockTree, specProvider, LimboLogs.Instance);
+            PoSSwitcher poSSwitcher = new(new MergeConfig(), new SyncConfig(), new MemDb(), blockTree, specProvider, new ChainSpec(), LimboLogs.Instance);
 
             Assert.That(poSSwitcher.TerminalTotalDifficulty, Is.EqualTo(expectedTtd));
             Assert.That(specProvider.MergeBlockNumber?.BlockNumber, Is.EqualTo(101));
@@ -93,7 +93,7 @@ public void Override_TTD_and_number_from_merge_config()
             IBlockTree blockTree = Substitute.For<IBlockTree>();
             TestSpecProvider specProvider = new(London.Instance);
             specProvider.UpdateMergeTransitionInfo(100, 20);
-            PoSSwitcher poSSwitcher = new(new MergeConfig() { TerminalTotalDifficulty = "340", TerminalBlockNumber = 2000 }, new SyncConfig(), new MemDb(), blockTree, specProvider, LimboLogs.Instance);
+            PoSSwitcher poSSwitcher = new(new MergeConfig() { TerminalTotalDifficulty = "340", TerminalBlockNumber = 2000 }, new SyncConfig(), new MemDb(), blockTree, specProvider, new ChainSpec(), LimboLogs.Instance);
 
             Assert.That(poSSwitcher.TerminalTotalDifficulty, Is.EqualTo(expectedTtd));
             Assert.That(specProvider.MergeBlockNumber?.BlockNumber, Is.EqualTo(2001));
@@ -106,7 +106,7 @@ public void Can_update_merge_transition_info()
             IBlockTree blockTree = Substitute.For<IBlockTree>();
             TestSpecProvider specProvider = new(London.Instance);
             specProvider.UpdateMergeTransitionInfo(2001, expectedTtd);
-            PoSSwitcher poSSwitcher = new(new MergeConfig() { }, new SyncConfig(), new MemDb(), blockTree, specProvider, LimboLogs.Instance);
+            PoSSwitcher poSSwitcher = new(new MergeConfig() { }, new SyncConfig(), new MemDb(), blockTree, specProvider, new ChainSpec(), LimboLogs.Instance);
 
             Assert.That(poSSwitcher.TerminalTotalDifficulty, Is.EqualTo(expectedTtd));
             Assert.That(specProvider.MergeBlockNumber?.BlockNumber, Is.EqualTo(2001));
@@ -254,7 +254,7 @@ private void AssertFinalTotalDifficulty(long ttd, long genesisDifficulty, long?
             SyncConfig syncConfig = new();
             if (pivotTotalDifficulty != null)
                 syncConfig = new SyncConfig() { PivotTotalDifficulty = $"{(UInt256)pivotTotalDifficulty}" };
-            PoSSwitcher poSSwitcher = new PoSSwitcher(new MergeConfig(), syncConfig, new MemDb(), blockTree, specProvider, LimboLogs.Instance);
+            PoSSwitcher poSSwitcher = new PoSSwitcher(new MergeConfig(), syncConfig, new MemDb(), blockTree, specProvider, new ChainSpec() { Genesis = genesisBlock }, LimboLogs.Instance);
             if (expectedFinalTotalDifficulty != null)
                 poSSwitcher.FinalTotalDifficulty.Should().Be((UInt256)expectedFinalTotalDifficulty);
             else
@@ -266,7 +266,7 @@ private static PoSSwitcher CreatePosSwitcher(IBlockTree blockTree, IDb? db = nul
         {
             db ??= new MemDb();
             MergeConfig? mergeConfig = new() { };
-            return new PoSSwitcher(mergeConfig, new SyncConfig(), db, blockTree, specProvider ?? MainnetSpecProvider.Instance, LimboLogs.Instance);
+            return new PoSSwitcher(mergeConfig, new SyncConfig(), db, blockTree, specProvider ?? MainnetSpecProvider.Instance, new ChainSpec(), LimboLogs.Instance);
         }
     }
 }
diff --git a/src/Nethermind/Nethermind.Merge.Plugin.Test/Synchronization/BeaconHeadersSyncTests.cs b/src/Nethermind/Nethermind.Merge.Plugin.Test/Synchronization/BeaconHeadersSyncTests.cs
index 8006941d498..1d9bdcbd1ae 100644
--- a/src/Nethermind/Nethermind.Merge.Plugin.Test/Synchronization/BeaconHeadersSyncTests.cs
+++ b/src/Nethermind/Nethermind.Merge.Plugin.Test/Synchronization/BeaconHeadersSyncTests.cs
@@ -18,6 +18,7 @@
 using Nethermind.Merge.Plugin.InvalidChainTracker;
 using Nethermind.Merge.Plugin.Synchronization;
 using Nethermind.Specs;
+using Nethermind.Specs.ChainSpecStyle;
 using Nethermind.State.Repositories;
 using Nethermind.Synchronization;
 using Nethermind.Synchronization.FastBlocks;
@@ -71,7 +72,7 @@ public IBeaconPivot BeaconPivot
 
         private PoSSwitcher? _poSSwitcher;
         public PoSSwitcher PoSSwitcher => _poSSwitcher ??= new(MergeConfig, SyncConfig, MetadataDb, BlockTree,
-                MainnetSpecProvider.Instance, LimboLogs.Instance);
+                MainnetSpecProvider.Instance, new ChainSpec(), LimboLogs.Instance);
 
         private IInvalidChainTracker? _invalidChainTracker;
 
diff --git a/src/Nethermind/Nethermind.Merge.Plugin/MergePlugin.cs b/src/Nethermind/Nethermind.Merge.Plugin/MergePlugin.cs
index 2213acad4e9..eebb8fc2b17 100644
--- a/src/Nethermind/Nethermind.Merge.Plugin/MergePlugin.cs
+++ b/src/Nethermind/Nethermind.Merge.Plugin/MergePlugin.cs
@@ -92,6 +92,7 @@ public virtual Task Init(INethermindApi nethermindApi)
                 _api.DbProvider.GetDb<IDb>(DbNames.Metadata),
                 _api.BlockTree,
                 _api.SpecProvider,
+                _api.ChainSpec,
                 _api.LogManager);
             _invalidChainTracker = new InvalidChainTracker.InvalidChainTracker(
                 _poSSwitcher,
diff --git a/src/Nethermind/Nethermind.Merge.Plugin/PoSSwitcher.cs b/src/Nethermind/Nethermind.Merge.Plugin/PoSSwitcher.cs
index fe860873b6c..632d4716a8f 100644
--- a/src/Nethermind/Nethermind.Merge.Plugin/PoSSwitcher.cs
+++ b/src/Nethermind/Nethermind.Merge.Plugin/PoSSwitcher.cs
@@ -12,6 +12,7 @@
 using Nethermind.Db;
 using Nethermind.Logging;
 using Nethermind.Serialization.Rlp;
+using Nethermind.Specs.ChainSpecStyle;
 
 namespace Nethermind.Merge.Plugin
 {
@@ -39,6 +40,7 @@ public class PoSSwitcher : IPoSSwitcher
         private readonly IDb _metadataDb;
         private readonly IBlockTree _blockTree;
         private readonly ISpecProvider _specProvider;
+        private readonly ChainSpec _chainSpec;
         private readonly ILogger _logger;
         private Hash256? _terminalBlockHash;
 
@@ -55,6 +57,7 @@ public PoSSwitcher(
             IDb metadataDb,
             IBlockTree blockTree,
             ISpecProvider specProvider,
+            ChainSpec chainSpec,
             ILogManager logManager)
         {
             _mergeConfig = mergeConfig;
@@ -62,6 +65,7 @@ public PoSSwitcher(
             _metadataDb = metadataDb;
             _blockTree = blockTree;
             _specProvider = specProvider;
+            _chainSpec = chainSpec;
             _logger = logManager.GetClassLogger();
 
             Initialize();
@@ -98,7 +102,9 @@ private void LoadFinalTotalDifficulty()
             }
             else
             {
-                UInt256 genesisDifficulty = _blockTree.Genesis?.Difficulty ?? 0;
+                if (_chainSpec?.Genesis == null) return;
+
+                UInt256 genesisDifficulty = _chainSpec.Genesis.Difficulty;
                 if (genesisDifficulty >= TerminalTotalDifficulty) // networks with the merge in genesis
                 {
                     _finalTotalDifficulty = genesisDifficulty;
diff --git a/src/Nethermind/Nethermind.Synchronization.Test/BlockDownloaderTests.Merge.cs b/src/Nethermind/Nethermind.Synchronization.Test/BlockDownloaderTests.Merge.cs
index 2800d2910bd..10ae29c0c92 100644
--- a/src/Nethermind/Nethermind.Synchronization.Test/BlockDownloaderTests.Merge.cs
+++ b/src/Nethermind/Nethermind.Synchronization.Test/BlockDownloaderTests.Merge.cs
@@ -20,6 +20,7 @@
 using Nethermind.Merge.Plugin.Synchronization;
 using Nethermind.Merge.Plugin.Test;
 using Nethermind.Specs;
+using Nethermind.Specs.ChainSpecStyle;
 using Nethermind.Stats;
 using Nethermind.Stats.Model;
 using Nethermind.Synchronization.Blocks;
@@ -456,6 +457,7 @@ public MergeConfig MergeConfig
             MetadataDb,
             BlockTree,
             SpecProvider,
+            new ChainSpec(),
             LimboLogs.Instance);
 
         protected override IBetterPeerStrategy BetterPeerStrategy => _betterPeerStrategy ??=
diff --git a/src/Nethermind/Nethermind.Synchronization.Test/SyncServerTests.cs b/src/Nethermind/Nethermind.Synchronization.Test/SyncServerTests.cs
index 5394cd8e754..8ecab27bc76 100644
--- a/src/Nethermind/Nethermind.Synchronization.Test/SyncServerTests.cs
+++ b/src/Nethermind/Nethermind.Synchronization.Test/SyncServerTests.cs
@@ -22,6 +22,7 @@
 using Nethermind.Merge.Plugin.Handlers;
 using Nethermind.Merge.Plugin.InvalidChainTracker;
 using Nethermind.Specs;
+using Nethermind.Specs.ChainSpecStyle;
 using Nethermind.Specs.Forks;
 using Nethermind.State;
 using Nethermind.Stats.Model;
@@ -180,6 +181,7 @@ public void Terminal_block_with_lower_td_should_not_change_best_suggested_but_sh
                 new MemDb(),
                 localBlockTree,
                 testSpecProvider,
+                new ChainSpec(),
                 LimboLogs.Instance);
             HeaderValidator headerValidator = new(
                 localBlockTree,
@@ -389,6 +391,7 @@ private Context CreateMergeContext(int blockTreeChainLength, UInt256 ttd)
                 new MemDb(),
                 localBlockTree,
                 testSpecProvider,
+                new ChainSpec(),
                 LimboLogs.Instance);
             MergeSealEngine sealEngine = new(
                 new SealEngine(new NethDevSealEngine(), Always.Valid),
diff --git a/src/Nethermind/Nethermind.Synchronization.Test/SynchronizerTests.cs b/src/Nethermind/Nethermind.Synchronization.Test/SynchronizerTests.cs
index a1ed58c7617..3d2cfd28eef 100644
--- a/src/Nethermind/Nethermind.Synchronization.Test/SynchronizerTests.cs
+++ b/src/Nethermind/Nethermind.Synchronization.Test/SynchronizerTests.cs
@@ -324,7 +324,7 @@ ISyncConfig GetSyncConfig() =>
                 {
                     mergeConfig.TerminalTotalDifficulty = UInt256.MaxValue.ToString(CultureInfo.InvariantCulture);
                 }
-                PoSSwitcher poSSwitcher = new(mergeConfig, syncConfig, dbProvider.MetadataDb, BlockTree, new TestSingleReleaseSpecProvider(Constantinople.Instance), _logManager);
+                PoSSwitcher poSSwitcher = new(mergeConfig, syncConfig, dbProvider.MetadataDb, BlockTree, new TestSingleReleaseSpecProvider(Constantinople.Instance), new ChainSpec(), _logManager);
                 IBeaconPivot beaconPivot = new BeaconPivot(syncConfig, dbProvider.MetadataDb, BlockTree, _logManager);
 
                 TrieStore trieStore = new(stateDb, LimboLogs.Instance);